P0156 code and check fuel cap light

I have been noticing poor acceleration on my truck and also will sometimes stick on the 4,500 rpm's and once I let off the gas it will shift. I have had the transmission serviced and no issues. I know the P0156 code is O2 sensor so I plan on replacing both down stream sensors since they go in pairs. I did have the truck on a lift for an exhaust issue earlier today and see the one wire is melted post catalytic converter so the parts are on the way. Could a bad catalytic converter come up as a P0156 or will this solve the issue? Thanks in advance.